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New Member

PBR's detection of the next hop availability

Hi,

I have configured PBR to create a backup interface. This is done by using a catch all ACL and setting two next hops in the map. It seems to work OK. But I am trying to understand what PBR tests in order to check if the highest priority next hop is available or not? Any clues?

TIA

ALan

4 REPLIES

Re: PBR's detection of the next hop availability

Hi Alan

The router checks for the availabilty of the next hop in the routing table.

The next hop will be generally installed in the routing table as a connected route.

When the link goes down this route is removed from the routing table and causes the PBR to look for the routing entry for the next hop specified and forwards the packet if it finds one.

Note:- this happens only when the next hop specified is directly conencted. If the next hop is not on a directly connected interface you need to configure recursive PBR.

Check out the following link for configuring recursive PBR

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a008021de72.html

HTH, rate if it does

Narayan

New Member

Re: PBR's detection of the next hop availability

Hi,

When the far end of the link is taken out of service by ifdown command, the router reports it as UP/UP and hence does not remove the connected route from the routing table.

Re: PBR's detection of the next hop availability

Hi Alan,

We can use PBR with multpile hops tracking feature. You can use tracking to verify the next hop IP address before forwarding the traffic to the next hop.

http://www.cisco.com/en/US/tech/tk364/technologies_configuration_example09186a0080211f5c.shtml

HTH,Please rate if it does.

-amit singh

Re: PBR's detection of the next hop availability

Alan,

Is your WAN conenction being handed over to you on ethernet?

This could be a problem as ethernet does not have any management like LMI in FR and hence will be up if the connection to the MUX/switch is up eventhough your far end is down.

In this case you have to use object tracking as suggested by amit

HTH

Narayan

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